1. Field of the Invention
The present invention relates to a data display unit mounted on a bicycle by which running data such as the running speed, the running time, the running distance etc. of a bicycle are calculated and displayed.
Particularly, the present invention relates to an improvement in the manners of display in a data display unit for a bicycle in which a microcomputer is incorporated to process the input data supplied from a sensor so that determined data such as the running speed etc. may be displayed.
2. Description of the Prior Art
A data display unit for a bicycle for making display of running data such as the running speed, the running distance and the like generally comprises a revolution detecting sensor for detecting the number of revolutions of a wheel and a main body of the display unit for calculating the running speed, the running distance and the like based on a signal from the revolution detecting sensor.
A revolution detecting sensor in general was, in the past, connected to a main body of a display unit by a release wire and the like so that a rotating block provided in the sensor may be mechanically rotated directly by the wheels. However, recently, in order that load may not be applied to a driving system of a bicycle and that the number of revolutions may be detected more accurately, a so-called magnet sensor or a photoelectronic sensor has been utilized as a revolution detecting sensor.
In the U.S. Pat. No. 4,074,196 for example, it is disclosed that a sensor comprising a photoelectronic sensor, a magnetic sensor or a Hall device can be utilized as a revolution detecting sensor. The U.S. Pat. No. 4,156,190 discloses an example of a photosensor as a revolution detecting sensor. These revolution detecting sensors are attached in association with the wheels.
A main body of a display unit having close relation with the present invention is disclosed for example in the U.S. Pat. No. 4,007,419 which comprises a circuit for calculating the running speed, the running distance and the like based on a revolution signal provided from a revolution detecting sensor and also comprises a liquid crystal display for indicating the running speed, the running distance and the like. Such a main body of a data display unit is mounted on a desired position near the handle or any other suitable position where the rider of the bicycle can easily see the display.
Such a data display unit generally comprises a revolution sensor and a main body and the main body of the display unit calculates the running distance and the like based on the signals supplied from the revolution detecting sensor. As described above, a photoelectronic sensor, a magnetic sensor or a Hall device sensor can be utilized as a revolution detecting sensor. If the revolution detecting sensor is a magnet sensor for example, it is structured by a magnet fixed in a rotating wheel and a lead switch fixed in a wheel supporting member so that the lead switch detects change in the position of the magnet according to the relative positional relation between the magnet and the lead switch, namely, the revolution of the wheel. As a result, if deviation is caused in the relative positional relation between the magnet and the lead switch, the revolution detecting sensor cannot detect the correct number of revolutions.
Accordingly, if it can be determined in the main body of the display unit whether or not the detection signal from the revolution detecting sensor is applied normally, it will be unnecessary to worry about any positioning errors or displacement of the revolution detecting sensor. In such a case, if the revolution detecting sensor should be in trouble during the running of the bicycle, such trouble can be immediately perceived.
A conventional display unit does not have a display function for such determination and it is only by change in the display of the running speed for example that it can be determined whether or not the detection signals from the revolution detecting sensor are applied normally.
In addition, if such a conventional display unit has a plurality of data display functions and that one selected kind of data is being displayed it cannot be determined in such a display unit whether or not the data other than the displayed data are correctly detected, namely, whether or not the detection signal is applied normally from the revolution detecting sensor.